Posted
by
CowboyNealon Thursday May 27, 2004 @06:25PM
from the sudden-climate-changes dept.

colonist writes "SPACE.com reports that most dinosaurs were incinerated within hours by the 'heat pulse' of an asteroid impact 65 million years ago. The study 'Survival in the first hours of the Cenozoic' presents a scenario where the only survivors were underground or were underwater in swamps or oceans. All unprotected creatures were 'baked by the equivalent of a global oven set on broil.'"

DirectionsPlace the dinosaurs in an oven-safe planet. Shake the seasonings until all the dinosaurs are evenly covered with a light layer of iridium. On top of that, shake on a little bit of garlic spice (not too much since it is salt). On top of that, add a few hearty shakes of chili powder to cover the animals lightly. Place the planet in the oven on the broil setting. It's important to place the planet in the middle of the oven so that it is not too close to the top broilers or it will burn. Let the dinosaurs cook for about 15 minutes on one side or until they start to get a little bit crisp. Flip the dinosaurs over in the planet and spice the back side like you spiced the front. Toss them back in the oven for another 10 minutes or until slightly crisp. Pull the planet out of the oven and flip the dinosaurs over a few times in the juice.

Gas Mark is just a heat setting for gas ovens / hobs. Basically a measure of the rate of gas being burnt as far as I am aware. It is an older measurement really, before reliable temperature probes - controlling gas input in a recipe is easier than measuring temperature on those old gas ovens.

Gas Mark 9 for example was extremely hot, around 250 degrees C or more. Gas Mark 1 would be "warm up some buns" or something.

Roast just means to cook in an oven. To broil something means to expose it to intense heat. It's the highest heat setting on an oven, and you're supposed to put the meat right beside the burners themselves.

Hmm, considering there's a dish called "London Broil", it just makes me wonder if that's not actually British, but yet another American bastardization...

A recent asteroid impact article on/. pointed out something that I had never thought of before. The two worst places to be after a major impact are under the impact and on the opposite side of the planet from it. Why is this? The debris that the impact throws up will travel out from the site of impact and some bits will go a long ways and other bits not so far. In any case, if you are 1/4 of the circumference of the earth from the site the debris can only come from one direction, but if you are 1/2 the circumference of the earth from the impact (opposite side of the earth) debris will be coming in from all directions. Some won't make it that far and some will fly even further, but it is the most likely place to get hit.

This is easy to visualize if you imagine a strike at the North Pole and the debris traveling along the lines of longitude to the South Pole.

"There's no question over whether an asteroid hit. The roughly 6-mile-wide (10-kilometer) space rock carved out the Chicxulub crater off Mexico's Yucatan Penninsula."

But fairly recently there was another article posted on slashdot, about the alleged impact having occurred in (what is now) Australia. (check, e.g., here http://www.msnbc.msn.com/id/4969840/ for a similar story.)

so what is the consensus *really*, in the scientific community? or is there just none?

the consensus is:
The asteroid that killed off the dinosaurs is the one that hit in the Yucatan Penninsula
The asteroid that killed off 99.9% of life before the dinosaurs existed was the one that hit near austrailia

I think you're talking about two different mass die-offs. The Yucatan crater theoretically caused the Late Cretaceous die-off (approx. 65 million years ago) that made the dinosaurs go extincet. The Australian crater has been linked to the Late Permian die-off, which happened about 250 million years ago.

So, Racer X, the scientific community would appear to have two consensuses (consenses? WTF?), one on each of the two issues.

Mass extinctions are a fairly regular event in the Earth's geologic history. There are at least two more, besides the Permian and Cretaceous catastrophes, with which I'm familiar. Most people only get taught about the Cretaceous one in high school, though, so they never hear about the others.

Kind of like the Ice Age. Up until I was 16, I only thought there was one. Turns out there were a shitload of them.

You are confusing two different craters. The Chicxulub crater is generally considered responsible for the KT (Cretaceous/Tertiary) extinction that killed of the dinosaurs.
The newly alleged impact crater off of Australia (there's still controversy over whether it is, in fact, an impact crater as opposed to the remnant of a volcano) is being considered as a cause of the P/T (Permian/Triassic) extinction that happened approximately 251 million years ago.
The Permian extinction is notable for being the largest mass extinction on record. Some 95% of all species apparently died out in less than a million years (how much less is a source of controversy). This compares to only 50% for the K/T extinction.

Of course I didn't read the article, as I don't subscribe and am lazy, but wouldn't the heat kill all the plants too? And I thought there were "many" survivors. Mostly small animals, besides plants and lower life forms. And how could 1 impact effect the entire planet with such a high amount of heat? Wouldn't that metemorph rocks as well? Or even react the atmosphere?

Plus, if it were that powerful to bake animals, would not the water temperature rise, and the air bake the animals which did survive, and destroy the birds as they're not too good about going underwater, and melt the ice at the caps, and...

Sorry, but this theory doesn't even sound plausible. What could they base it on? (Sorry, article/.'ed)

A brief heat pulse wouldn't raise the water temperature much, but even a rise of a few degrees might cause a number of more sensitive species to die off. Which may well be what happened.

I don't know about the birds, but this is hardly a fatal objection. Small animals can find many hiding places unavailable to larger ones. I don't think we need be too surprised if a number of smaller dinosaur species survived.

There were no polar ice caps during the Mesozoic.

I'd be shocked to discover that space.com's servers were ever overloaded by/. If you don't want to read the article, then say so. (If you're referring to the original paper, you can only get the abstract without a paid subscription anyway.)

Plus, if it were that powerful to bake animals, would not the water temperature rise, and the air bake the animals which did survive, and destroy the birds as they're not too good about going underwater, and melt the ice at the caps, and...

To kill most large animals, the air doesn't need to be hot enough to bake the whole animal, just ruin its lungs.

Plants are easy. Many (most?) plants have evolved mechanisms to allow them to survive forest fires, brush fires and the like. The root stock would survive, and the seeds are mixed with soil/blown into protected places etc. Remember, they don't all have to survive, just enough to repopulate the species. There would be myriad places where plants or animals would be sheltered by the shape of a canyon/cave or whatever.

There are quite a few bird species that live in burrows/caves/hollow logs etc which would have survived. There are a lot of bird species that respond to any danger by diving into the water, and diving deep. Grebes, cormorants, and the like. There are lots of diving birds.

As far as raising the temperature of the water, you're vastly underestimating the amount of energy it would take to raise the temperature of all of the earth's oceans. It takes a lot more energy to raise the temperature of a volume of water than it takes to raise the same volume of air the same amount. (any physicists/chemists/engineers want to run the numbers?) The surface temperature of the oceans would probably rise a bit, then most of that energy would be shed back into the atmosphere by evaporation. The overall temp of the oceans would remain pretty constant, certainly not enough to melt the ice caps. For the superheated air directly above the glaciers, there would probably be a little bit of surface melting, which would immediately refreeze, leaving a glazed surface.

To be more exact for your "a lot of energy" required to raise water over the air - it is about 4 times as much energy for water than air. That is because the specific head of fresh water is 1 (Ocean water is.93) while the specific heat of air is only.25. Thus it takes 4 times as much energy to raise 1g of water 1 degree Celcius as compared to a gram of air.

This doesn't at all take into the account the fact that the starting temperature of the air is higher than that of the water. The average temperature of water in the oceans is just a bit above freezing in the pole areas and is about 17C(62F) on average (max 36C). The average temperature of air is much higher due to being over landmasses. Thus heating all of the air is MUCH easier than water.

And how could 1 impact effect the entire planet with such a high amount of heat?

It was a very large impact. They estimate an object 10km in diameter, which left a crater 200km in diameter. They believe that material ejected during the impact actually reached suborbital altitudes and that much of the heat was generated by the friction of re-entry.

Wouldn't that metemorph rocks as well?

From the space.com article: "Previous work uncovered a global layer of material that had melted and then hardened when the impact vaporized terrestrial rock."

Or even react the atmosphere?

Not sure what you mean by that. They think the energy involved would have heated the atmosphere enough to cause widespread death, but that would require temperatures 100 degrees C.

So many things survived from that time other than the Dinosaurs. Large trees, many forms of reptiles and mammals that are virtually the same (based on fossil records) to this day.

Not too mention that the fossil records for Dinosaurs don't stop on 1 day.

It seems that the Doomsday theory gets more headlines than other theories suggesting, disease and climate change (a much slower, more boring process) were the cause. Even though the damage of a meteor strike would have been far more devastating and left the planet set back near square one as far as life.

If the earth was baked and then the sun was blocked by smoke and ash, how come so much survived?

Exactly! Evolution put a lot of effort (so to speak) into evolving seeds that refuse to germinate unless the conditions are just right. Germinating only when conditions are right maximises the chance of survival for the plant.

I had a packet of cactus seeds with instructions to soak them in very hot water for one minute, plant them immediately afterwards in moist sandy soil and leave them in the dark for a week or so. Even so, mine didn't germinate until three weeks later. Fussy little bug

Is how they ever managed to live in the first place. The strength of muscles is a function of the area of their cross-section. It increases only roughly at a rate of the square of its size. Weight goes up as a cube of its size. Things get heavier much faster than they get stronger.

And just how much stronger could dino muscles have been than modern mammalian muscle? 140% stronger, 170%? That's really stretching it, and it still isn't nearly enough.

Land animals probably can't be much bigger than an elephant.

And no, I'm not a christian scientist. I don't think it's a conspiract, the bones are there, and they show how big the things must have been. I'd just like answers (prefereably those that don't have anything to do with superstitious bible crap).

And just how much stronger could dino muscles have been than modern mammalian muscle? 140% stronger, 170%? That's really stretching it, and it still isn't nearly enough.

I think you're underestimating how strong many animals really are. Our close relatives, the chimpanzees, are considerably stronger, pound-for-pound, than we are. Reptiles are also noted for being very muscular, even if they don't have much stamina.

There is a theory that the earth was lighter back then, which let heavier animals thrive. It's an interesting theory - it also says that the Pangea continent covered the whole earth (not just one side) since the earth was ~40% of it's current size, and that it grew by collecting space debris over time. Someone should do the math concerning muscle efficiency and this ancient mass of the earth and see if it works out.

But the fact is, that land animals larger than elephants have, in fact, existed. Mass does indeed go up as a cube of length, but land animals (dinosaurs included) aren't just cubes of flesh and bone. If you take the large amount of non-solid space in the lungs and gastro-intestinal system, you do reduce the density, and therefore the mass by an extent.

There is quite a bit of research going on in this area that relates to dinosaurs. I don't have any specific refs, but if you check out the recent literature, you should be able to find a number of current articles.

And just how much stronger could dino muscles have been than modern mammalian muscle? 140% stronger, 170%? That's really stretching it, and it still isn't nearly enough.

When doing comparisons be careful to avoid human muscle. Humans are cursorial hunters (jogging after their prey until it collapses from heat exhaustion.) Most of their muscles are set up to only use a few percent of their fibers at a time - and switch to another batch when the first run out.

That's why hysterical strength is so much greater: Under great stress you CAN use your whole muscle power for a few contractions - like a mother lifting a car off her kid (a rather common event, actually). But it comes at a cost: The bones, pads between them, and muscle attachments are NOT built to the necessary strength for this. Use of hysterical strength normally means some serious, often permanent, injury.

Most other animals (including even our close relatives the chimps) use a much higher fraction of their muscles all the time - or under only moderate provocation - and have the structure to support this use. (That's why they're so dangerous to people who handle them without having armor on and weapons handy.)

Land animals probably can't be much bigger than an elephant.

Not if they're going to be chased around by lion prides, packs of canids, and humans. (The square-cube law also applys to dumping heat.) You can build a workable animal MUCH bigger than an elephant. But now that there are warmbloods specializing in running things to collapse and eating them you can't keep a population of things that large viable in the wild.

I'm still confused on why *all* the Dinosaurs died 65 million years ago, yet the rest of land animals (amphibians, reptiles, mammals, and birds) survived.

Dinosaurs weren't all big dumb lumbering brutes -- some were as small as our present-day reptiles and amphibians, and had mostly the same environment. Ne'ermind that at least one of the reptiles had a brain/body mass ratio better than a wolf.

So why did every dinosaur die but reptiles survived? Why did every dinosaur die but birds survived?

Just a few weeks ago, the theory surfaced that the asteroid impact was only a factor in the demise of the dinosaurs (the dust caused the earths temperature to drop just a few degrees for several years -- which is a big deal if you're a reptile, but not so much if you're a mammal). Now there's a new theory that says the dinosaurs were burned alive. Next week, there will be another theory.

Personally, I'd like for these theories to go through a bit more critical review before they're broadcast to the public. This smacks as sensationalism more than science.

The really large asteroids can kick up up billions of tons of sulfur and other materials into the atmosphere. This can cause prolonged darkness for about half a year after the collision. The resulting darkness cause global temperatures to plunge near freezing. The COLD not the HEAT could result in large scale extinctions, including the dinosaurs

Unfortunately the linked article is available in the Online Journal which you can either subscribe to or go to you neareast Uni Library and check it out.

A Thermal heat pulse and the ejecta from the impact could travel around the world because of gravity dragging the ejecta back towards the earth. Upon reentry, the ejecta emitted IR radiation, brightening the sky globally. This means no night and no shadows (as the heat sources were distributed across the sky compared with the single-source solar IR radiation). This means there was nowhere to hide unless you were underground. Even rock crevices were no shelter. Subsequent fires igniting simultaenously [the suggest that there are isotopically uniform charcoal deposits at the boundary] would have added to the carnage. These fires were not significant compared to the intensity of the IR radiation. Normal solar flux ~1.4kW.m^-2, this event was calucated by Melosh in a previous paoer in 1990 to product ~10kW.m^-2. Note that ambient air temerature would have only rise ~10 K.

As for survivors, those burrowers > 10cm below the soil surface would survive. Sheltering and semi-aquatic birds are posited to be survivors.

The important thing is that this paper presents no specific fossil evidence. It does offer some phylogenetic evidence to support the bird survival hypothesis. It presents one model that can be further refined and/or refuted with evidence. It is not necessarily true or false but it can be falsified. They suggest checking Gondwanan sites for evidence of spherules (proof of ejecta reentering) and their distribution. That is the nature of science which the majority of posters thus far need to grasp. Think of science in terms of mathematical functions that approach a limit/converge as evidence and models accumulate.

The new study reviewed existing geologic evidence for the known impact and considered interesting patterns in species survival. How did some birds, mammals, crocodiles, snakes and other animals endure the calamity that wiped out larger species?

That's a good question. But it's got a bug in it - the phrase "wiped out larger spieces". Better to say - selectively wiped out one branch of animals that came in all shapes and sizes, and lived in all kinds of environments right alongside animals that *didn't* die out.

That asteroid sure was amazing!

The survivors burrowed underground or were protected from the firestorm by swamps or oceans, says study leader Doug Robertson of the University of Colorado at Boulder. The details were published in the May-June issue of the Bulletin of the Geological Society of America.

That's so plainly idiotic that it beggars belief. Dinosaurs came in a wide variety of sizes, some smaller than chickens. And there were many aquatic animals that also became extinct, that supposedly would have been safe according to this "study leader".

Another win for the hypothesis that makes for a good special effect, then. And published by the Geological Society - well colour me not suprised.

Actually it's well accepted as by far the most likely candidate for what happened. By the way, other theories include the theory of gravity, relativity theory etc... all pretty much proven, ask Hiroshima about E=mc^2 if you don't believe that one:P

"Actually it's well accepted as by far the most likely candidate for what happened."

In the general public's mind perhaps, but not elsewhere. There is a LOT of fossil evidence showing that Chicxulub did NOT wipe out the dinos. There is also fossil evidence that dinos were already in decline BEFORE Chicxulub hit.

Before and after Chicxulub Earth was experiencing a lot of volcanic activity. So much in fact, that the compositiom of the atmosphere was changing. As I recall the oxygen content was reducing from 30% down to 24% (I'm sure these are not the exact numbers, but they are close). Less oxygen meant that animals had to work harder in take in the same amount of oxygen. The dinos may have have suffocated.

> Before and after Chicxulub Earth was experiencing a lot of volcanic activity. So much in fact, that the compositiom of the atmosphere was changing. As I recall the oxygen content was reducing from 30% down to 24% (I'm sure these are not the exact numbers, but they are close).

Funny, no. But sometimes that kind of dramatic analogy is necessary to get the point across to people who don't understand what the word "theory" means in a scientific context.

I tend to personalize it a bit: "If you believe that ___* is 'just a theory,' be aware that gravity is 'just a theory' as well. I invite you to try jumping off a skyscraper because, surely, nothing that is 'just a theory' can hurt you."

*___ is almost always evolution, of course, though sometimes it's relativity.

Nope, the fact that you fall if you jump off a skyscraper is that fact that you fall if you jump off a skyscraper. Gravity is the theory that says you fall because the Earth, being rather large, exerts a powerful attractive force on your soon-to-be corpse. You could just as easily explain the falling by using the Aristotelian (IIRC) "things fall because it is their nature to fall" -- but that theory proved to be incompatible with the evidence, and thus was discarded; modern gravitational theory is the best we've got, so far.

Actually, the fact that you fall if you jump off a skyscraper is the fact of gravity.

You are assuming that you know what will happen in some unobserved (hypothetical) event. Either you are Psychic, or you are using some theory that seems to have been useful in the past to predict what will happen in the situation you propose.

Whaddayaknow? You were using the theory of gravity. (the fact of gravity that you speak of is strictly for chumps)

There's plenty of evidence of evolution out there. I'll go ahead and choose the easiest to see: bacteria. There's a reason that penicillin (and other antibiotics) don't work much any more. The bacteria they used to kill have developed an immunity to their effects. One might even go so far as to say they evolved into a new form of species that is immune/resistant to the effects of antibiotics. There's some evidence for you right there.

Evolution can never be proven by science. And that goes for the entire array of evolutionary theories.

Domestication is a form of evolution. By man learning and practicing husbandry of animals and selecting desirable traits he (he in the generic sense) exerted specific pressures on large based familial lines. Thus was eventually born our concept of breeds. The blue heeler was bred for herding ability, the greyhound for running, the poodle as a dare (?). nearly every trait that a modern dog has is genetica

Domestication is by artificial selection. That theory some people disagree with isn't really called evolution the way Darwin wrote it, it's much more properly called natural selection. This is to distinguish it from at least one major theory of evolution that has been very largely disproved only in the last century(Lamark's Theory of eveolution by inheritance of acquired characteristics, see also Lysinkoism), and may be necessary to distinguish it from some other variants still floating around in the zeitge

The development pathway that unites all animals includes a stage in which a viable (usually fertilised) egg cell (zygote) divides a number of times to form a ball of cells (morula, blastula) gradually differentiating because of (dorsal/ventral etc.) gradients in (HOX) gene expression.

Sponges (porifera) are a likely candidate for the oldest surviving animal lineage, potentially dating from the recently annointed Ediacaran [slashdot.org]

Well accepted doesn't make it correct. It's still a theory, and one (I might add) that cannot be proven, unlike a few others you've quoted.

Unlike in some circles, well accepted means no has yet found evidence against it in science. Not, we all beleive it to be true. When someone has evidence against it, it becoem a disproved theory is the evidence is strong enough. However the theory of evolution has had no credible evidence against it, neither has gravity, or thermodynamics. Only small addendums.

I have faith in Christ. I need not refute scientific evidence to support my faith. God is wonderfull, sometime msyterious, and I needn't beleive in fairies ot beleive in God. Why should I beleive in creationist theories when the evolution theory fits my faith just fine.

But it doesn't. Just in case you missed it: Evolution does not fit your faith, if that faith is God and Christ. If one of the foundations (creationism) of your hypothesis (God and Christ are real) is wrong, then the whole thing is simply WRONG. You can't throw one away and replace it with another.

Cool. An anonymous coward knows more than the Pope about religion. Arrogant, aren't we?

The Pope stated sometime in the 1980s that christianity and evolution don't contradict, and that one can easily believe in

Unfortunately this is replying to an AC, but hopefully this thread is still live enough for others to read this.

The AC says:

There's a lot to know about being Christian (really a lot to read), but it all relates to two fundamental rules or commandments:

1. One must love GOD more than anything else.
2. One must love others like oneself.

The AC, is in fact, quite mistaken. What he quoted here is not the core tenet of Christianity; this is just a nice way to live with God thrown in for good measure. What Christianity is is this:

God and mankind had a good releationship, but this relationship was broken because people choose to live without acknowledging God. People are incapable of reconciling this relationship, so God, because He loves people, sent His son Jesus Christ to die on the cross and suffer horribly as a reconciliation so we can have a restored relationship with God. The restored relationship with God is what allows people to actually succeed in loving others and God...

That is the core of Christianity; not the Pope, not communion, not hymns, not going to church every week, not even the Bible. You can verify this for yourself, it's not some "theory" about Christianity - you should be quite able to go pick up a Bible and read it and you should see this is the case, and if you are so inclined, I'd recommend it.

As a man who has decided to commit himself to Christ, I kind of am distressed and saddened by the fact that people do not really understand my faith and lump it in with "you narrow-minded American Christian!". Especially since I am a scientist, love physics, and don't see a conflict between evolution and a universe created by God (if God is all powerful, why can't He use evolution?)

Anyway, at least I hope that you have an understanding now that the common perceptions of "Christianity" might not be universally accurate. Another instance of "don't believe everything you see on TV! (or read on/.!)"

If, 5 milliseconds after I die, I believe anything at all, then I will be surprised and change my opinions based on the new evidence. If a vengeful God chooses to damn me for not feeling the same way throughout my life despite lack of evidence, then screw Him.

No offence, but my wife was declaired dead for almost two minutes about 5 years ago. What did she see? Nothin'. She thought she had simply fallen asleep. The one thing she does remember is that her chest hurt like hell from the electrodes though.

Granted, she's only one data point, and I'm sure you will discount her experience. But I thought I'd share it anyway.

Everything in science is a theory. The "asteroid impact" idea has a lot to back it up however since there are some realy big craters on this ball of mud we call home. Check out the 170 km one at the Yucatan Peninsula [solarviews.com].

All science is to some extend bassed on layers of theory, however each new theory, if correctly done, explains all the known facts but often includes elements of predictions along the lines of "If this theory is correct we will expect to see X".

Now we can go looking for X and if we find it and the prediction was somewhat unexpected before the theory was proposed it is a strong indication of its validity.

Case in points Einsteins prediction of light being bend by high gravity object that was indeed confi

In common usage a theory is often viewed as little more than a guess or a hypothesis. But in science and generally in academic usage, a theory is much more than that. A theory is an established paradigm that explains all or many of the data we have and offers valid predictions that can be tested. In science, a theory can never be proven true, because we can never assume we know all there is to know. Instead, theories remain standing until they are disproven, at which point they are thrown out altogether or modified slightly.

Isn't the whole "asteroid impact" scenario a theory? Doesn't that make this new theory a theory based on a theory?

It is widely accepted that an asteroid fell down around 65 million years ago and that this approximately coincided with the end of the dinosaurs (except for birds). You will not find a single serious scientist who disagrees with this.

What is more controversial is how quickly they died off and if it was only because of the asteroid or if other factors were involved as well. This latest cla

"Alvarez Hypothesis" is the term used to describe the idea that dinosaurs died as a result of a catastrophic asteroid impact. I do not believe that the hypothesis has attained the status of theory, however.
The main evidence for such a hypothesis seems to come from the observation of geologist Walter Alvarez of a significant layer of Iridium on the Cretaceous-Tertiary boundary (KT boundary), due to the fact that Iridium is a very rare element on Earth but found in abundance in asteroids and meteorites.
This link [priweb.org] has some more information along with Wikipedia [wikipedia.org].

Or, indeed, how actual dinosaurs are still around [geocities.com], and have remained unchanged for the past 80 million years.

Now true, tuataras are burrowing animals, but they have to leave their burrows to feed on the insects they love so much.

Don't even get me started on birds. This theory has so many holes in it. If the Earth was grilled as the report suggest, then where's the geological evidence? A thin layer of carbon circa 65 million years ago representing all the burnt land flora?

1. Do the Americans really have enough nukes to destroy the world ten times over?

This one I hear a lot. First of all, despite what you may have heard, really the majority of the energy of a nuclear explosion turns into heat and blast immediately, NOT radiation. The only exception to this is the so-called Neutron bomb, designed specifically with radiation (more specifically fast neutrons and gamma rays) in mind. But realistically, although the Americans have built approximately 70,000 warheads of almost 70 different types, they now possess a stockpile of around 9600 warheads. Surprising as it may sound, this is NOT enough to 'destroy' the world. Even hitting every city in the world with everything in every country's arsenal would not be able to 'destroy' the world. The world is still aBIG place. Keep in mind the Russians have around the same numbers of warheads.

Surprising as it may sound, this is NOT enough to 'destroy' the world.

You're assuming that 9600 warheads detonated together would 'only' amount to 9600 times the results of one warhead detonation. This is by no means a widely accpeted view. It's much more likely that there is a "tipping point" where the damage from a nuclear exchange cascades into a catastrophe for the species (us).In any event, I prefer not to prove it conclusively, Dr. Strangelove.

Even hitting every city in the world with everything in every country's arsenal would not be able to 'destroy' the world.
The whole problem is that people are vague about what they mean when they say 'destroy the world.' A full-scale nuclear war would definitely

kill vast numbers of people immediately in the cities of the countries that fought

kill vast numbers of people everywhere else in those countries, because there wouldn't be trucks driving into town to deliver groceries to the supermarket.

What is it about people (anti-nuke types in particular) that they feel the need to exaggerate the horrors of nuclear war? I suppose it's just wishful thinking on their part: if (for example) there were exactly enough nukes to "destroy the entire world", it would be impossible to justify building any additional warheads.

I'd counter their argument with the possibility that there are other worlds for us to destroy too and planning for only ONE is lazy. Heh, silly short-sighted anti-nuke people!

For those of you not in the military, this means that if the bodies of the dead were to get up again, we could kill them all 12 more times. We humans are capable of creating a much larger catastrophe than our often theoretical cousins in space; and it's saddening.

The fact that man has the power to potentially do something shouldn't make you sad. It should actually make you proud. Now, if man would actually do it, that would be sad.

Man can kill man, but until they do, there is nothing to be sad about.

I'll tell you the problem with the scientific power that you're using here. It didn't [re]quire any discipline to attain it. You read what others have done and you took the next step. You didn't earn the knowledge for yourself so therefore you don't take any responsibility for it. You stood on the shoulders of geniuses to accomplish something as fast as you could and before you even knew it you had it.

So you only "earn" the "right" to make a product if you personally developed every single scientific t

Think about it. The rest are not carbon, if there is complete incineration, then only some non carbonic element are left (Ca, OS, etc...). If the frying is not complete, the bacteria in the body then start their work and eat up the corpse. As for baking on the other side of the world, it really depend on the energy of the impact. It heat up the atmosphere which then in a heat wave travel around the globe. Whether the heat wave is enough is another question which the article seems to answer : yes.

I couldn't read it THIS time (because the server is slashdotted). But I did read it - or another describing the same theory - when it first became newsworthy some years ago.

There's plenty of evidence for it.

First off, the prediction comes straight out of physical modeling of what happens when a big asteroid hits:

- A bunch of rocks are kicked every which way.
- If the asteroid is big enough a LOT of them go into space.
- A fraction of them have enough energy to get above the atmosphere but not achieve escape velocity.

Once you realize those three things, it's straightforward for a physicist to calculate, for various size impacts on various sites (land, shallow ocean, deep ocean), how MUCH mass goes up, how MUCH of it comes back down, WHERE it comes down, HOW FAST it comes down, and what the results are.

So they calculated that. And came to the conclusion that for impacts of a certain range of sizes the result would be several hours of a rain of sand, all over the Earth, at speeds of up to several miles per second (plus rains of rocks of varying density at different distances from the crater and its antipode). The sky becomes essentially solid meteor trails for hours.

And those are HOT! Hot enough to dry out most of the plants and set them afire. Hot enough to kill any animal life on the surface that can't get underground or under water right away and then stay there for hours.

So if the sky turned into a broiler oven over the whole Earth for several hours all at once, what does this predict? One hemisphere is day and the burrowing nocturnals survive, the other is night and the burrowing diurnals survive. (And in particular regions it got REALLY hot, or REALLY shocked by the primary impact or the secondary rain of rocks, and NOTHING survived).

So they looked at the fossil record and that's what they found. Prediction confirmed - very good evidence for the model. Further, they could now tell WHAT TIME OF DAY the impact occurred and roughly where.

Then they looked in the area where this model predicted the impact should have been and FOUND A CRATER of the correct size (along with plenty of other evidence that this PARTICULAR crater's impact coincided with the extinction event).

Looks solid to me. Unless something new comes up I consider the puzzle of the extinction events solved.

Looks solid to me. Unless something new comes up I consider the puzzle of the extinction events solved

I presume you mean "extinction event", not "events". There have been a few mass extinctions, not all caused by impacts.

Anyway, there's a lot of evidence to indicate that something probably hit the Earth, yes. The puzzle that remains is why it only affected the dinosaurs.

Remember, they were all sizes and lived in all kinds of environments, so saying things like "the smaller animals did such-and-such" also includes the smaller dinosaurs. We don't have any small dinosaurs running around today (or even large ones - assuming that they would have kept their capacity for diversifiation and speciation if even some had survived) so there was obviously more to it than "something big hit the Earth".

That is the remaining puzzle - and nobody has been able to even come close to solving it that I've heard. I'd be interested to hear of anyone who has, though!